This invention relates to a method and apparatus for heating non-flammable gases. More particularly, the method and apparatus of this invention pertains to heating air so that any liquid water that may be present therein is vaporized before the air is used in various applications, e.g. spray painting. The present invention can be used for many different applications.
The present invention is a significant improvement over the prior art. For example, U.S. Pat. No. 3,737,626 teaches a heating device having a housing with partitions, an electric heating unit located within one partition, a metallic coiled tubing surrounding the heating unit, supply means for admitting compressed air to one end of the coiled tubing, a filter casing with filter elements positioned within another partition, the filter casing being connected to the other end of the coiled tubing, exhaust means for carrying the dry, cleaned, and heated compressed air to the point of use, and electrical control means for the energization of the heating unit.
Of particular significance, U.S. Pat. No. 3,737,626 discloses that the heating unit has a temperature responsive sensing means positioned into the space between partitions of a housing. Thus, the temperature responsive sensing means measures the temperature of the air surrounding the coiled tubing and does not directly measure the actual temperature of the air within the coiled tubing which is being heated. The filter casing with filter elements is located at the outlet end of the coiled tubing to remove, among other things, any liquid water which was not vaporized by the heating unit. Although this technique has some advantages, it still requires a filtering system to remove liquid water which was not vaporized by the heating unit before the heated air is ready for its intended use.
U.S. Pat. No. 4,147,923 teaches a heating device having a housing having first and second compartments, an electric heating unit located centrally, first and second chambers, wherein the second compartment serves as a storage means for condensation formed in the first chamber, inlet means for admitting compressed air into the first chamber, outlet means for removing the compressed air from the second chamber, and electrical control means for controlling the degree of energization of the heating unit in response to the temperature of the heated air inside the second chamber. Although this technique has the advantage of directly measuring the temperature of the heated air, it requires a system for collecting and storing condensation. Furthermore, this technique also teaches the use of a filter means to remove liquid water which was not vaporized by the heating unit before the heated air is ready for its intended use.
The present invention retains the benefits of the prior art devices described above while eliminating the need for filtering or condensation systems to remove liquid water from the heated non-flammable gas, such as air, before the heated non-flammable gas is ready for its intended use.
U.S. Pat. No. 1,946,262 teaches a hand-operated hot air gun having a thermostat enclosed within a separate compartment in the gun barrel to prevent overheating of the device without increasing the time necessarily required to heat an electric heating element also within the hand-operated gun. Although this apparatus has some advantages, it requires treatment of the air within the hand-operated gun just prior to being dispensed through an outlet nozzle. Since the heating element is enclosed within the hand-operated gun, this apparatus increases safety hazards and renders the hand-operated gun more difficult to maneuver because it will be heavier and more cumbersome than it would be without the enclosed heating element and thermostat. The present invention completely eliminates the need for a heating element and thermostat within a hand-operated gun.
Thus, the present invention involves the discovery of the source not before known of a long-standing problem and the application of the remedy for that problem. Specifically, the present invention involves the discovery of the source of the long-standing problem of heating a non-flammable gas without the need for filtering systems, condensation systems, or problems associated with a heating element and thermostat enclosed within a hand-operated applicator gun. The source of the long-standing problem was inaccurate temperature measurement of the gas being heated and the inefficient temperature control of that gas before the gas was transferred to a hand-operated applicator gun.
The present invention applies a remedy for that problem by providing an elongated preheating tubing section having an outlet end connected to the inlet end of the coiled tube to provide non-flammable gas to the inlet end of the coiled tube and electrical control means operatively connected to a temperature responsive sensing means positioned at the inlet end of the helical tubing and in direct contact with the gas for sensing the actual temperature of the gas so that electric heating means will vaporize any liquid water present in the gas before the gas is tranferred to a hand-operated applicator gun.